The present invention relates to a polymer composition having positive temperature coefficient characteristics of the electric resistance and more particularly to a polymer composition having positive temperature coefficient characteristics which can withstand high voltage and further which when used as a heat generator, produces a uniform distribution of heat, has a long service life and thus can be utilized as an overcurrent-protecting element or a heat generator.
Compositions prepared by compounding electrically conductive particles such as carbon black to crystalline polymers or inorganic substances such as barium titanate are known to have the positive temperature coefficient characteristics that an electric resistance value abruptly increases when the temperature reaches a specified temperature range (see, for example, Japanese Patent Publication Nos. 33707/1975 and 10352/1981).
These conventional compositions are useful as overcurrentprotecting elements or heat generators. When, however, they are used under relatively high voltage conditions or unexpected overvoltage is applied thereto, they cannot withstand such relatively high voltage or unexpected overvoltage and thus break down.